Modern consumer electronics, such as smart phones, personal digital assistants, and location based services devices, as well as enterprise electronics, such as servers and storage arrays, are packing more integrated circuits into an ever shrinking physical space with expectations for decreasing cost. Every new generation of integrated circuits with increased operating frequency, performance and the higher level of large scale integration have underscored the need for back-end semiconductor manufacturing to provide more solutions involving the integrated circuit itself. Numerous technologies have been developed to meet these requirements. Some of the research and development strategies focus on new package technologies while others focus on improving the existing and mature package technologies. Both approaches may include additional processing of the integrated circuits to better match the targeted package.
Miniaturization of electronic circuits is a goal in virtually every field, not only to achieve compactness in mechanical packaging, but also to decrease the cost of manufacture of the circuits. Many digital and analog circuits, including complex microprocessors and operational amplifiers, have been successfully implemented in silicon based integrated circuits (ICs). These circuits typically include active devices such as bipolar transistors and field effect transistors (FETs), diodes of various types, and passive devices such as resistors and capacitors.
One area that remains a challenge to miniaturize are radio frequency (RF) circuits, such as those used in cellular telephones, wireless modems, and other types of communication equipment. The problem is the difficulty in producing good inductors and capacitors in silicon technologies that are suitable for RF applications. Attempts to integrate inductors into silicon technologies have yielded either inductor Q values less than five or required special metalization layers such as gold. The integration of capacitors has been slightly more successful, but the tolerance and size remain an issue. With cost pressures on integrated circuit products, yield issues associated with integrated passive devices and the cost of special metallization layers are not acceptable.
It is well known that the direct current (DC) resistance of a metal line that forms a spiral inductor is a major contributor to the inductor Q degradation. One way to reduce this effect is to use wide metal line-widths, however, this increases the inductor area and the parasitic capacitance associated with the structure. The larger inductor area limits the miniaturization that can be achieved, and the parasitic capacitance associated with the larger area decreases the self-resonance frequency of the inductor, thereby limiting its useful frequency range. Also, since the Q is directly proportional to frequency and inversely proportional to the series loss of the inductor, the metal line widths cannot be chosen arbitrarily large.
Thus, a need still remains for integrated passive device system for radio frequency applications. The demand for wireless products, makes it is increasingly critical that answers be found to these problems. In view of the ever-increasing commercial competitive pressures, along with growing consumer expectations and the diminishing opportunities for meaningful product differentiation in the marketplace, it is critical that answers be found for these problems. Additionally, the need to save costs, improve efficiencies and performance, and meet competitive pressures, adds an even greater urgency to the critical necessity for finding answers to these problems.
Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.